This application relates, in general, to a method for controlling computer network security. More specifically it relates to an easily alterable or expandable method for computer network security which controls information flow on the network from/to external and internal destinations.
Connectivity and security are two conflicting objectives in the computing environment of most organizations. The typical modern computing system is built around network communications, supplying transparent access to a multitude of services. The global availability of these services is perhaps the single most important feature of modern computing solutions. Demand for connectivity comes both from within organizations and from outside them.
Protecting network services from unauthorized usage is of paramount importance to any organization. UNIX workstations, for example, once connected to the Internet, will offer all the services which it offers another station on the next table to the entire world. Using current technology, an organization must give up much of its connectivity in order to prevent vulnerability, even to the extent of eliminating all connections to the outside world or other sites.
As the need for increased security grows, the means of controlling access to network resources has become an administrative priority. In order to save cost and maintain productivity, access control must be simple to configure and transparent to users and applications. The minimization of setup costs and down time are also important factors.
Packet filtering is a method which allows connectivity yet provides security by controlling the traffic being passed, thus preventing illegal communication attempts, both within single networks and between connected networks.
Current implementation of packet filtering allows specification of access list tables according to a fixed format. This method is limited in its flexibility to express a given organization's security policy. It is also limited to the set of protocols and services defined in that particular table. This method does not allow the introduction of different protocols or services which are not specified in the original table.
Another method of implementing packet filtering is tailoring the computer operating system code manually in every strategic point in the organization. This method is limited by its flexibility to future changes in network topology, new protocols, enhanced services and to future security threats. It requires a large amount of work by experts modifying proprietary computer programs, making it insufficient and expensive to setup and maintain.